1. Field of the Invention
The present invention relates to a process of preparing at least one of perfluoroalkylcarboxylic acids, for example, perfluorooctylcarboxylic acid.
2. Description of the Related Art
Perfluoroalkylcarboxylic acids are industrially useful compounds as feedstocks for surface-active agents, water-and oil-repellant agents, and medicines and agricultural chemicals. Conventional processes of preparing these compounds are generally as follows:
(1) Electrolytic fluorination process using a hydrocarbon compound as a feedstock, PA1 (2) Production process by the reaction of fuming sulfuric acid and perfluoroalkyliodide, PA1 (3) Production process by the reaction of perfluoroalkyliodide and carbon dioxide, PA1 (4) Oxidative decomposition process using an oxidant such as a dichromate or a permanganate in which a perfluoroalkylolefin is used as a feedstock (see for example, Japanese Patent Kokoku Publication No. 7691/1969), PA1 (5) Ozonolysis process using a perfluoroalkylolefine as a feedstock (see for example, Japanese Patent Kokai Publication No. 64051/1974), and PA1 (6) Oxidative decomposition process using a ruthenium catalyst and perfluoroolefin in a fluorocarbon solvent (see Journal of Fluorine Chemistry, 13 (1979), pages 175-177).
However, the above exemplified processes have the following disadvantages: for example, a low reaction yield; necessity of severe conditions such as a low reaction temperature from -70.degree. C. to -40.degree. C. or a high reaction temperature from 150.degree. C. to 200.degree. C.; and necessity of use of a corrosive or hazardous reagent or involving difficulties in after-treatment or recovery due to using a metal compound, so that they can not be always effective processes. In particular, the above process (6) has a disadvantage that reaction rate remarkably decreases when water phase exists in the reaction system, so that such a process are not practically applicable for a system containing water phase.